Donate Help Contact The AHA Sign In Home
American Heart Association
Circulation
Search: search_blue_button Advanced Search
Circulation. 1998;98:1085-1091

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tam, S. H.
Right arrow Articles by Nakada, M. T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tam, S. H.
Right arrow Articles by Nakada, M. T.

(Circulation. 1998;98:1085-1091.)
© 1998 American Heart Association, Inc.


Clinical Investigation and Reports

Abciximab (ReoPro, Chimeric 7E3 Fab) Demonstrates Equivalent Affinity and Functional Blockade of Glycoprotein IIb/IIIa and {alpha}vß3 Integrins

Susan H. Tam, MS; Patricia M. Sassoli, BS; Robert E. Jordan, PhD; ; Marian T. Nakada, PhD

From Centocor, Malvern, Pa.

Correspondence to Marian T. Nakada, PhD, Centocor, 200 Great Valley Pkwy, Malvern, PA 19355. E-mail nakadam{at}centocor.com


*    Abstract
up arrowTop
*Abstract
down arrowIntroduction
down arrowMethods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Background—Large, randomized, and blinded clinical trials (EPIC, EPILOG, and CAPTURE) have demonstrated that abciximab (ReoPro, chimeric 7E3 Fab) markedly reduces thrombotic events associated with percutaneous transluminal coronary interventions. The marked early benefits at 30 days were sustained at 6 months and 3 years. Initially developed because of its efficacy in blocking GP IIb/IIIa ({alpha}IIb3) receptors on platelets, abciximab also binds with equivalent affinity to {alpha}vß3.

Methods and Results—This study presents a detailed characterization of the {alpha}vß3 interaction, including the ability of abciximab to (1) bind with comparable affinity to {alpha}vß3 and GP IIb/IIIa, (2) inhibit {alpha}vß3 and GP IIb/IIIa–mediated cell adhesion in vitro with IC50 values approximating binding KD values, and (3) redistribute between GP IIb/IIIa and {alpha}vß3 integrins in vitro.

Conclusions—As an antagonist of not only GP IIb/IIIa but also {alpha}vß3, abciximab may provide additional clinical benefit in preventing {alpha}vß3-mediated effects such as thrombin generation, clot retraction, or smooth muscle cell migration and proliferation. Abciximab binds with equivalent affinity to both GP IIb/IIIa and {alpha}vß3 and redistributes between the 2 integrin receptors in vitro. Abciximab has been previously shown to circulate on platelets for up to 2 weeks. Taken together, these findings suggest that abciximab may have the ability to inhibit both GP IIb/IIIa and {alpha}vß3 for extended periods.


Key Words: glycoproteins • antibodies • platelet aggregation inhibitors


*    Introduction
up arrowTop
up arrowAbstract
*Introduction
down arrowMethods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Abciximab, an approved agent for use in patients undergoing percutaneous coronary intervention, is an effective antithrombotic agent because of its ability to bind to glycoprotein (GP) IIb/IIIa ({alpha}IIb3) and potently inhibit platelet aggregation. EPIC,1 EPILOG,2 and CAPTURE,3 3 large, randomized, double-blinded, placebo-controlled trials, demonstrated that abciximab is safe and effective in reducing the number of thrombotic ischemic events after percutaneous coronary intervention. The parental form of abciximab, murine 7E3 IgG (m7E3 IgG), was also shown (at a single high concentration) to bind to a related integrin, {alpha}vß3,4 also known as the vitronectin receptor. The {alpha}vß3 receptor is expressed on platelets,5 osteoclasts,6 tumor cells,7 and endothelial8 and smooth muscle cells9 and is upregulated during angiogenesis10 and wound healing.11 Functions of this receptor include cell adhesion,4 proliferation,7 and migration12 ; bone resorption6 ; and platelet-mediated thrombin generation.13

Murine 7E3 IgG (at single high concentrations) has been previously shown to inhibit (1) {alpha}vß3-mediated cell and platelet adhesion,4 5 (2) {alpha}vß3-mediated sickle red blood cell adherence to human umbilical vein endothelial cells (HUVECs),14 (3) vitronectin-coated bead binding to endothelial cells,15 (4) adhesion of GP IIb/IIIa–expressing cells to HUVECs,16 and more recently (5) angiogenesis in an in vivo SCID mouse-human skin model.17 The purpose of this study was to provide a more complete characterization of the affinity, cell type, and species specificity of binding of abciximab to {alpha}vß3 and to determine more quantitatively the effect of abciximab on {alpha}vß3-mediated effects.


*    Methods
up arrowTop
up arrowAbstract
up arrowIntroduction
*Methods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Binding to Purified {alpha}vß3
{alpha}vß3 was purified from M21 melanoma cells kindly provided by Dr Joseph Jakubowski (Eli Lilly, Indianapolis, Ind) and coated at 0.5 µg/mL onto 96-well Linbro plates (Flow/ICN) for 2 hours at room temperature and blocked. Abciximab was iodinated with Iodobeads (Pierce Chemicals), diluted in HEPES-buffered saline with calcium (HBSS, JRH Bioscience) containing 1 mmol/L MgCl2, added to {alpha}vß3-coated wells, and incubated for 4 hours at 37°C. Wells were washed, and bound radioactivity was counted in a gamma counter. Data were analyzed by nonlinear regression with GraphPad Prism. Statistics were performed with the 2-tailed Student's t test.

Cell Type and Species Cross-Reactivity
Primary human cell lines and growth media were purchased from Clonetics Corp. Cells were grown to confluence, and [125I]abciximab in M199 media (JRH Bioscience) containing 10% FCS and 0.02% azide was added to the cells and incubated for 2 hours at 37°C. Cells were washed, and bound radioactivity was quantified and analyzed as described. Primary cell lines from nonhuman sources were purchased from Cell Systems, rat aortic smooth muscle cells were a gift from Dr G. Stouffer (University of Texas, Medical Branch, Galveston, Tex), and established cell lines were from ATCC. Murine 7E3 IgG was added to confluent cells and incubated for 2 hours at 37°C. [125I]anti-mouse secondary antibody [goat anti-mouse IgG F(ab')2, 1 µCi/µg, Jackson ImmunoResearch] was used to detect m7E3 IgG.

Cell Adhesion
Vitronectin (Collaborative Biomedical Products) at 5 µg/mL was coated on 96-well ELISA plates for 2 hours at room temperature and blocked. M21 cells were labeled with 111In (DuPont/NEN) for 15 minutes in the presence of 400 nmol/L tropolone (Sigma Chemical Co). Washed cells were resuspended in HBSS and incubated with antibody for 4 hours at 37°C. Anti-{alpha}vß5 (GIBCO) monoclonal antibody ascites clone P1F6 was used at 1:3000 dilution when indicated. Cells were added to vitronectin-coated plates and incubated for 1 hour at 37°C. Plates were washed twice, and bound radioactivity was quantified with a gamma counter. For human erythroleukemia (HEL) cell adhesion, cells were labeled with 0.15 µg/mL calcein (Molecular Probes) for 15 minutes at 37°C and washed. Assay plates were read on a Labsystems Fluoroskan II plate reader and analyzed as described.

Redistribution Studies
HEL cells (expressing GP IIb/IIIa) or M21 cells (expressing {alpha}vß3) were labeled with FITC-abciximab (20 µg/mL for 30 minutes) and washed. An equal number of FITC-abciximab–labeled and unlabeled cells were added and incubated at 37°C on a rotator at 300 rpm. At various times, cells were removed and fixed with 1% formaldehyde for 5 minutes at room temperature. Fixed samples were diluted and analyzed on a Becton Dickinson FACScan flow cytometer. Dual-label experiments were performed to demonstrate the heterologous redistribution of abciximab from GP IIb/IIIa to {alpha}vß3 and vice versa. HEL cells either were labeled with FITC-abciximab and washed or were sequentially labeled with 10E5 IgG (anti–GP IIb/IIIa, Centocor), treated with R-phycoerythrin (RPE)–goat anti-mouse F(ab')2 (Accurate Chemical and Scientific Corp), and fixed with 1% formaldehyde. M21 cells either were labeled with FITC-abciximab or were sequentially labeled with A10 IgG (anti-{alpha}vß3, Centocor) and RPE–goat anti-mouse F(ab')2 and then fixed. Fixation of the cells prevented the detection antibody from dissociating from cells during the experiment. Heterologous cells labeled with FITC or RPE were mixed and incubated, and at various times, cells were removed, fixed with 1% formaldehyde, diluted, and analyzed by flow cytometry. Redistribution was assessed by the ability of FITC-abciximab to equilibrate from the RPE-negative cells to the RPE-positive cells.


*    Results
up arrowTop
up arrowAbstract
up arrowIntroduction
up arrowMethods
*Results
down arrowDiscussion
down arrowReferences
 
Saturation binding experiments (Table 1Down) revealed that the affinity of abciximab for HUVECs (KD=9.8±2.7 nmol/L) was similar to that for purified {alpha}vß3, (KD=11.0±3.2 nmol/L) and to GP IIb/IIIa on platelets (KD=6.2±2.7 nmol/L). Binding experiments revealed an {approx}2-fold difference in the total number of antibodies binding at saturation for HUVECs (Bmax=490 000±160 000 sites per cell for abciximab, 210 000±89 000 sites per cell for m7E3 IgG), consistent with the monovalent binding of abciximab and bivalent binding of m7E3 IgG observed previously for platelets.18 The binding to monolayer cultures represented receptors accessible to the antibody, although preliminary experiments that showed comparable maximal binding of abciximab to monolayer versus suspension cultures suggested that the Fab fragment bound to both luminal and abluminal receptors. The actual number of abciximab binding sites on HUVECs reported here does not necessarily reflect the level of expression in vivo because the cultured cells used were continually proliferating. Because cells were grown in FCS, it was possible that endogenous ligands occupied {alpha}vß3 receptors and affected the affinity or receptor number bound by abciximab. Acid treatment of HUVECs to remove potentially bound ligand from {alpha}vß3 receptors did not affect the affinity or Bmax of abciximab binding (data not shown). The {alpha}vß3 receptor can exist in different activation states.19 20 21 The ability of abciximab to recognize both the inactive and active conformation of {alpha}vß3 was suggested by the fact that PMA, which has been shown to activate {alpha}vß3,20 did not affect the affinity or receptor number of abciximab binding (data not shown). Unfortunately, the absence of an activation-dependent positive control antibody in this experiment precludes a definitive conclusion.


View this table:
[in this window]
[in a new window]
 
Table 1. Abciximab Binding to and Blocking of GP IIb/IIIa and {alpha}vß3

Abciximab binding to HUVECs was competitively inhibited by LM609 IgG, an {alpha}vß3 complex–dependent antibody (Figure 1Down). Negative control antibody 10E5 IgG, which binds to GP IIb/IIIa but does not recognize {alpha}vß3, and MT412 Fab, a chimeric Fab fragment that binds to CD4, did not compete for abciximab binding (Figure 1Down), thereby demonstrating the specificity of abciximab binding to {alpha}vß3.



View larger version (20K):
[in this window]
[in a new window]
 
Figure 1. Competition binding of antibodies with [125I]abciximab for binding to HUVECs. HUVECs were incubated with 1 µg/mL [125I]abciximab in the presence of increasing concentrations of unlabeled competitor. LM609 binds to {alpha}vß3, 10E5 binds to GP IIb/IIIa, and MT412 binds to CD4. Data points represent mean±SEM of triplicate determinations.

[125I]abciximab bound with similar affinity to a variety of human primary cell lines, including HUVECs, coronary artery endothelial cells, coronary artery smooth muscle cells, and skeletal muscle cells (Table 2Down). No binding was seen on keratinocytes or bronchial epithelial cells, which have been reported not to express {alpha}vß3.22 The species cross-reactivity profile of abciximab was determined by use of primary and established cell lines. Murine 7E3 IgG bound to cells from human, baboon, and rhesus monkey with relative high affinity (Table 3Down). Murine 7E3 IgG also bound to canine and rat cells but with only moderate affinity; it bound with even lower affinity to guinea pig cells. Murine 7E3 IgG did not bind to bovine, feline, or rabbit cells at concentrations as high as 20 µg/mL. These cells were determined to be positive for {alpha}vß3 expression by their reactivity with LM609 IgG.


View this table:
[in this window]
[in a new window]
 
Table 2. Cell Type Reactivity of 125I-Abciximab


View this table:
[in this window]
[in a new window]
 
Table 3. Species Cross-Reactivity Profile of Murine 7E3 IgG1

To determine the potency of abciximab inhibition of {alpha}vß3 and GP IIb/IIIa, cell adhesion experiments were performed with M21 melanoma cells that express {alpha}vß3 but not GP IIb/IIIa23 and with HEL cells that express GP IIb/IIIa but not {alpha}vß3.24 Cells were preincubated for 4 hours at 37°C with antibodies to ensure equilibrium binding of the antibodies. Subsequent experiments demonstrated that equilibrium was reached at 1 hour for abciximab and at 2 hours for m7E3 IgG, consistent with previous studies with 7E3 Fab and IgG binding to platelet GP IIb/IIIa.25 Abciximab and m7E3 IgG both inhibited M21 cell adhesion to vitronectin-coated plates (Figure 2ADown). LM609 IgG also blocked binding to a similar extent, whereas 10E5 IgG had no effect. Maximal inhibition seen with abciximab, m7E3 IgG, or LM609 IgG was not complete and reached only {approx}65%. Previous reports described an {alpha}vß5-mediated component of adhesion of M21 cells to vitronectin,26 so a polyclonal anti-{alpha}vß5 antibody was coincubated with the cells. This resulted in complete inhibition of M21 cell adhesion to vitronectin-coated plates by abciximab, m7E3 IgG, and LM609 IgG (Figure 2BDown). IC50 values were similar to those obtained in the absence of anti-{alpha}vß5. Indirect binding experiments using a secondary detection antibody suggested that M21 cells expressed one half the number of {alpha}vß5 receptors than {alpha}vß3 receptors and an equivalent number of ß1 and {alpha}vß3 integrins (data not shown). ß1 receptors did not appear to play a role in cell adhesion in this system because {alpha}vß3 and {alpha}vß5 antibodies together completely blocked cell adhesion. HEL cell adhesion to vitronectin-coated plates was similarly inhibited by abciximab, m7E3 IgG, and the GP IIb/IIIa–specific blocking antibody 10E5 (Figure 3Down). The IC50 values for blocking of {alpha}vß3 and GP IIb/IIIa–mediated cell adhesion by abciximab are shown in Table 1Up.



View larger version (33K):
[in this window]
[in a new window]
 
Figure 2. Effect of abciximab on {alpha}vß3-mediated M21 melanoma cell adhesion. M21 cells, expressing {alpha}vß3, were 111In-labeled, preincubated with antibody in the absence (A) or presence (B) of anti-{alpha}vß5, and added to vitronectin-coated plates. Unbound cells were removed and bound cells quantified with a gamma counter. Data are expressed as mean±SEM of duplicate determinations. IC50 values were calculated by nonlinear regression of data.



View larger version (15K):
[in this window]
[in a new window]
 
Figure 3. Effect of abciximab on GP IIb/IIIa–mediated HEL cell adhesion. HEL cells, expressing GP IIb/IIIa, were fluorescently labeled with calcein, preincubated with antibody, and added to vitronectin-coated plates. Unbound cells were removed and bound cells quantified with a Labsystems Fluoroskan II fluorescence plate reader. Data are expressed as mean±SEM of triplicate determinations.

Platelet-bound abciximab has been shown to move from platelet to platelet.27 28 A similar redistribution occurred between {alpha}vß3 and {alpha}vß3 and between {alpha}vß3 and GP IIb/IIIa, as examined with FACS analysis. FITC-conjugated abciximab was incubated with HEL cells that express GP IIb/IIIa but not {alpha}vß3. Cells were washed to remove unbound FITC-abciximab, and an equal number of unlabeled HEL cells were added. Bound FITC-abciximab was measured immediately after mixing and at the indicated intervals during the incubation. Results of a representative experiment are shown in Figure 4Down. At the time of mixing, 2 distinct populations were seen. With time, the fluorescence of the positive population (right) decreased (peak shifting to the left) and that of the negative population (left) increased (peak moving to the right), eventually resulting in complete merging of the 2 populations into a single, unimodal peak. The mean fluorescence at equilibrium (t=2 hours) was {approx}50% of the mean fluorescence of the original labeled cell population. In 3 separate experiments, a unimodal peak was apparent within 2 hours. Consistent with these findings, the t1/2 of [125I]abciximab dissociation from HEL cell GP IIb/IIIa was {approx}2 hours (data not shown).



View larger version (24K):
[in this window]
[in a new window]
 
Figure 4. Abciximab redistribution from GP IIb/IIIa to GP IIb/IIIa. An equal number of FITC-abciximab–labeled and unlabeled HEL cells expressing GP IIb/IIIa were combined and samples were removed at the indicated times, fixed, and evaluated by flow cytometry. At t=0, 2 separate peaks were observed for FITC-abciximab–labeled cells (right) and unlabeled cells (left). Both peaks merged into a uniform peak within 2 hours.

M21 cells that express {alpha}vß3 were used, and redistribution was observed from {alpha}vß3 to {alpha}vß3 (Figure 5Down). M21 cells that were bound with FITC-abciximab formed the peak on the right at t=0 in Figure 5Down, and the unlabeled M21 cells were seen as the peak on the left. Within 2 hours, both peaks merged, indicating that the FITC-abciximab dissociated and bound to available {alpha}vß3 sites on the unlabeled M21 cell population. The t1/2 of [125I]abciximab dissociation from {alpha}vß3 on M21 cells was {approx}2 hours (data not shown), similar to that observed for binding to GP IIb/IIIa.



View larger version (23K):
[in this window]
[in a new window]
 
Figure 5. Abciximab redistribution from {alpha}vß3 to {alpha}vß3. An equal number of FITC-abciximab–labeled and unlabeled M21 cells expressing {alpha}vß3 were combined, and samples were removed at the indicated times, fixed, and evaluated by flow cytometry. At t=0, 2 separate peaks were observed for FITC-abciximab–labeled cells (right) and unlabeled cells (left). Both peaks merged into a uniform peak within 2 hours.

Redistribution of FITC-abciximab between GP IIb/IIIa and {alpha}vß3 also occurred. The number of integrin receptors expressed on HEL cells and M21 cells was not equivalent. HEL cells expressed {approx}20 000 GP IIb/IIIa receptors per cell, whereas M21 cells expressed {approx}300 000 {alpha}vß3 receptors per cell. With this difference in receptor number, a unimodal peak would not be observed at equilibrium after redistribution. Therefore, a double-label technique was used that allowed determination of FITC-abciximab binding to each separate cell population. For redistribution from {alpha}vß3 to GP IIb/IIIa, M21 cells were bound with FITC-abciximab and mixed with unlabeled HEL cells. FITC-abciximab redistributed from the {alpha}vß3 on M21 cells to the GP IIb/IIIa on HEL cells (Figure 6Down). In the converse experiment, redistribution from GP IIb/IIIa to {alpha}vß3 was also demonstrated (Figure 7Down).



View larger version (20K):
[in this window]
[in a new window]
 
Figure 6. Abciximab redistribution from {alpha}vß3 to GP IIb/IIIa. HEL cells were incubated with 10E5 IgG, washed, incubated with RPE–goat anti-mouse F(ab')2, washed, and fixed. HEL cells were mixed with FITC-abciximab–bound M21 cells, and samples were removed at the indicated times, fixed, and evaluated by flow cytometry. Redistribution was assessed by the ability of FITC-abciximab to equilibrate from the RPE-negative M21 cells to RPE-positive HEL cells.



View larger version (21K):
[in this window]
[in a new window]
 
Figure 7. Abciximab redistribution from GP IIb/IIIa to {alpha}vß3. M21 cells were incubated with A10 IgG, washed, incubated with RPE–goat anti-mouse F(ab')2, washed, and fixed. M21 cells were mixed with FITC-abciximab–bound HEL cells, and samples were removed at the indicated times, fixed, and evaluated by flow cytometry. Redistribution was assessed by the ability of FITC-abciximab to equilibrate from the RPE-negative HEL cells to RPE-positive M21 cells.


*    Discussion
up arrowTop
up arrowAbstract
up arrowIntroduction
up arrowMethods
up arrowResults
*Discussion
down arrowReferences
 
Although the ability of abciximab to inhibit GP IIb/IIIa–mediated platelet aggregation is well characterized, the interaction and potential implications of abciximab binding to the related integrin {alpha}vß3 have not been extensively studied. This report documents the ability of abciximab to bind with comparable affinity to {alpha}vß3 and GP IIb/IIIa, to prevent {alpha}vß3 and GP IIb/IIIa–mediated cell adhesion, and to redistribute between GP IIb/IIIa and {alpha}vß3 integrins in vitro.

Abciximab bound to cell-expressed and purified {alpha}vß3 with an affinity that was comparable to its binding to GP IIb/IIIa. Abciximab bound to a variety of human cell lines with an affinity similar to that for purified {alpha}vß3. The species cross-reactivity profile of m7E3 IgG suggests that the use of abciximab in animal models in species lower than nonhuman primates is limited. The species cross-reactivity profile was done only with m7E3 IgG, which may not necessarily predict the affinity or efficacy of the monovalent abciximab in animal models. It is interesting to note that the cross-reactivity profile of abciximab with platelets (data not shown) mirrors the data generated here with {alpha}vß3-expressing vascular cells.

Abciximab effectively blocked {alpha}vß3- and GP IIb/IIIa–meditated cell adhesion. The IC50 values for inhibition in both assays were similar to the KD values for binding, suggesting that the ability of abciximab to block cell adhesion was directly proportional to the occupancy of {alpha}vß3 and GP IIb/IIIa receptors.

Previous studies have documented the ability of abciximab to redistribute in vitro27 and in vivo28 between platelets. This is attributed to the ability of the antibody to bind rapidly but reversibly to GP IIb/IIIa. This characteristic provides the drug with a long platelet-bound half-life, with antibody detected on platelets as long as 2 weeks after therapy.28 This occupancy is associated with a prolonged inhibition of platelet function in response to shear stress for up to 1 week.29 Because abciximab binds to both GP IIb/IIIa and {alpha}vß3 with similar affinity, it was reasonable to hypothesize that it could redistribute between the 2 receptors. Abciximab redistributed from GP IIb/IIIa to GP IIb/IIIa and from {alpha}vß3 to {alpha}vß3. Dual labeling was a useful method that allowed the concurrent study of 2 distinct cell populations. Experiments revealed that abciximab could redistribute between GP IIb/IIIa and {alpha}vß3. The kinetics of redistribution, which was complete in {approx}2 hours, was correlated with binding studies, which determined a dissociation half-life of {approx}2 hours for [125I]abciximab binding to GP IIb/IIIa or {alpha}vß3.

{alpha}vß3 has been reported to mediate cell attachment and spreading4 ; cell survival, migration, and proliferation7 9 10 ; intimal hyperplasia30 ; and angiogenesis.10 Platelets adhere to vitronectin through both GP IIb/IIIa and {alpha}vß35 , and agonist-stimulated platelets bind osteopontin through {alpha}vß321 , which may facilitate platelet adhesion to osteopontin-containing atherosclerotic lesions.31 {alpha}vß3 can also support clot retraction32 and a component of platelet-mediated thrombin generation.13 Thrombin formation by platelets was more effectively inhibited by 7E3 than by antibodies that block GP IIb/IIIa alone,13 suggesting that {alpha}vß3 was also capable of mediating thrombin generation. A recent report describes the ability of prothrombin to bind directly not only GP IIb/IIIa33 but also {alpha}vß3.20 This interaction facilitates thrombin formation, providing a possible mechanism for the observed inhibition of thrombin generation by 7E3. These data suggest an additional mechanism for abciximab efficacy, blockade of thrombin generation mediated by {alpha}vß3 expressed on vascular endothelium or smooth muscle cells exposed by vessel injury.

Although {alpha}vß3 receptors appear to mediate many biological processes, it is not clear if any of these can also be driven by receptors with overlapping functions or if they are actually blocked by abciximab in patients. The roles and levels of expression of {alpha}vß3 by circulating cells, including platelets and leukocytes, and by vascular cells, including endothelial and smooth muscle cells, in normal and disease states in humans are not completely clear. In addition, the accessibility and extent of blockade of {alpha}vß3 receptors by abciximab, especially within the vessel wall, are not known. In humans, at reduced bolus doses (0.15 mg/kg), 88±21% of the injected antibody was found to be platelet bound 2 hours after injection.34 Free abciximab was rapidly cleared from the circulation, and 1 hour after injection, <10% of the dose was detectable as free antibody.34 It has therefore been postulated that it is unlikely that a large pool of {alpha}vß3 exists that competes for abciximab binding. This suggests that although {alpha}vß3 receptors may be expressed and bound by abciximab, the total number of accessible {alpha}vß3 receptors in the normal vasculature is much smaller than GP IIb/IIIa receptor number.

This study provides in vitro evidence for the ability of abciximab to bind with high affinity to {alpha}vß3 and to prevent {alpha}vß3-mediated effects. In addition, we have shown that abciximab redistributes between both GP IIb/IIIa and {alpha}vß3 integrins in vitro. The redistribution of abciximab not only may provide prolonged efficacy for platelet-mediated effects but also may allow long-lived efficacy for {alpha}vß3-mediated effects. The physiological and clinical implications of {alpha}vß3 binding extend beyond the ability of abciximab to block platelet and vascular cell adhesion but suggest that abciximab may potentially continue to inhibit other {alpha}vß3-mediated functions involving cell migration, proliferation, and platelet-mediated thrombin generation long after cessation of therapy.


*    Acknowledgments
 
We gratefully acknowledge Drs Barry Coller and Harlan Weisman for helpful discussions, Dr John Ghrayeb for the purification of {alpha}vß3, Ellen Lance for technical advice, and Joanie Wendel for manuscript preparation.

Received January 27, 1998; revision received April 16, 1998; accepted May 1, 1998.


*    References
up arrowTop
up arrowAbstract
up arrowIntroduction
up arrowMethods
up arrowResults
up arrowDiscussion
*References
 

  1. The EPIC Investigators. Use of a monoclonal antibody directed against the platelet glycoprotein IIb/IIIa receptor in high-risk coronary angioplasty. N Engl J Med. 1994;330:956–961.[Abstract/Free Full Text]
  2. The EPILOG Investigators. Platelet glycoprotein IIb/IIIa receptor blockade and low-dose heparin during percutaneous coronary revascularization. N Engl J Med. 1997;336:1689–1696.[Abstract/Free Full Text]
  3. The CAPTURE Investigators. Randomized placebo-controlled trial of abciximab before and during intervention in refractory unstable angina: the CAPTURE study. Lancet. 1997;349:1429–1435.[Medline] [Order article via Infotrieve]
  4. Charo IF, Bekeart LS, Phillips DR. Platelet glycoprotein IIb-IIIa-like proteins mediate endothelial cell attachment to adhesive proteins and the extracellular matrix. J Biol Chem. 1987;262:9935–9938.[Abstract/Free Full Text]
  5. Coller BS, Cheresh DA, Asch E, Seligsohn U. Platelet vitronectin receptor expression differentiates Iraqi-Jewish from Arab patients with Glanzmann thrombasthenia in Israel. Blood. 1991;77:75–83.[Abstract/Free Full Text]
  6. Rodan SB, Rodan GA. Integrin function in osteoclasts. J Endocrinol. 1997;154:S47–S56.[Abstract]
  7. Montgomery AMP, Reisfeld RA, Cheresh DA. Integrin {alpha}vß3 rescues melanoma cells from apoptosis in three-dimensional dermal collagen. Proc Natl Acad Sci U S A. 1994;91:8856–8860.[Abstract/Free Full Text]
  8. Conforti G, Dominquez-Jimenez C, Zanetti A, Gimbrone MA Jr, Cremona O, Marchisio PC, Dejana E. Human endothelial cells express integrin receptors on the luminal aspect of their membrane. Blood. 1992;80:437–446.[Abstract/Free Full Text]
  9. Hoshiga M, Alpers CE, Smith LL, Giachelli CM, Schwartz SM. {alpha}vß3 Integrin expression in normal and atherosclerotic artery. Circ Res. 1995;77:1129–1135.[Abstract/Free Full Text]
  10. Brooks PC, Clark RA, Cheresh DA. Requirement of vascular integrin {alpha}vß3 for angiogenesis. Science. 1994;264:569–571.[Abstract/Free Full Text]
  11. Clark RAF, Tonnesen MG, Gailit J, Cheresh DA. Transient functional expression of {alpha}vß3 on vascular cells during wound repair. Am J Pathol. 1996;148:1407–1421.[Abstract]
  12. Liaw L, Skinner MP, Raines EW, Ross R, Cheresh DA, Schwartz SM, Giachelli CM. The adhesive and migratory effects of osteopontin are mediated via distinct cell surface integrins. J Clin Invest. 1995;95:713–724.
  13. Reverter JC, Béguin S, Kessels H, Kumar R, Hemker HC, Coller BS. Inhibition of platelet-mediated, tissue factor-induced thrombin generation by the mouse/human chimeric 7E3 antibody. J Clin Invest. 1996;98:863–874.[Medline] [Order article via Infotrieve]
  14. Sugihara K, Sugihara T, Mohandas N, Hebbel RP. Thrombospondin mediates adherence of CD36+ sickle reticulocytes to endothelial cells. Blood. 1992;80:2634–2642.[Abstract/Free Full Text]
  15. Zanetti A, Conforti G, Hess S, Martin-Padura I, Ghibaudi E, Preissner KT, Dejana E. Clustering of vitronectin and RGD peptides on microspheres leads to engagement of integrins on the luminal aspect of endothelial cell membrane. Blood. 1994;84:1116–1123.[Abstract/Free Full Text]
  16. Gawaz M, Neumann F-J, Dickfeld T, Reininger A, Adelsberger H, Gebhardt A, Schomig A. Vitronectin receptor ({alpha}vß3) mediates platelet adhesion to the luminal aspect of endothelial cells. Circulation. 1997;96:1809–1818.[Abstract/Free Full Text]
  17. Varner JA, Nakada M, Jordan R, Coller B. Anti-angiogenic properties of 7E3, an integrin ß3 subunit antagonist, in the SCID mouse-human skin model of human angiogenesis. Thromb Haemost. 1997;90(suppl):158. Abstract.
  18. Wagner CL, Mascelli MA, Neblock DS, Weisman HF, Coller BS, Jordan RE. Analysis of GP IIb/IIIa receptor number by quantification of 7E3 binding to human platelets. Blood. 1996;88:907–914.[Abstract/Free Full Text]
  19. Pelletier AJ, Kunicki T, Quaranta V. Activation of the integrin {alpha}vß3 involves a discrete cation-binding site that regulates conformation. J Biol Chem. 1996;271:1364–1370.[Abstract/Free Full Text]
  20. Byzova TV, Plow EF, Jacobs JJ. Interaction or prothrombin with activated {alpha}vß3 on vascular cells. Blood. 1997;90:286. Abstract.
  21. Bennett JS, Chan C, Vilaire G, Mousa SA, DeGrado WF. Agonist-activated {alpha}vß3 on platelets and lymphocytes binds to the matrix protein osteopontin. J Biol Chem. 1997;272:8137–8140.[Abstract/Free Full Text]
  22. Marchisio PC, Bondanza S, Cremona O, Cancedda R, DeLuca M. Polarized expression of integrin receptors and their relationship with cytoskeleton and basement membrane matrix in culture human keratinocytes. J Cell Biol. 1991;112:761–773.[Abstract/Free Full Text]
  23. Kieffer N, Fitzgerald LA, Wolf D, Cheresh DA, Phillips DR. Adhesive properties of the ß3 integrins: comparison of GP IIb-IIIa and the vitronectin receptor individually expressed in human melanoma cells. J Cell Biol. 1991;113:451–461.[Abstract/Free Full Text]
  24. Plow EF, Loftus JC, Levin EG, Fair DS, Dixon D, Forsyth J, Ginsberg NH. Immunologic relationship between platelet membrane GP IIb/IIIa and cell surface molecule expressed by a variety of cells. Proc Natl Acad Sci U S A. 1986;83:6002–6006.[Abstract/Free Full Text]
  25. Coller BS. Activation affects access to the platelet receptor for adhesive glycoproteins. J Cell Biol. 1986;103:451–456.[Abstract/Free Full Text]
  26. Wayner EA, Orlando, RA, Cheresh DA. Integrins {alpha}vß3 and {alpha}vß5 contribute to cell attachment to vitronectin but differentially distribute on the cell surface. J Cell Biol. 1991;113:919–929.[Abstract/Free Full Text]
  27. Christopoulos C, Mackie I, Lahiri I, Machin S. Flow cytometric observations on the in vivo use of Fab fragments of a chimeric monoclonal antibody to platelet glycoprotein IIb-IIIa. Blood Coagul Fibrinolysis. 1993;4:729–737.[Medline] [Order article via Infotrieve]
  28. Mascelli MA, Lance ET, Damaraju L, Wagner CL, Weisman HF, Jordan RE. Pharmacodynamic profile of short-term abciximab treatment demonstrates prolonged platelet inhibition with gradual recovery from GP IIb/IIIa receptor blockade. Circulation. 1998;97:1680–1688.[Abstract/Free Full Text]
  29. Konstantopoulos K, Kamat SG, Schafer AI, Banez EI, Jordan R, Kleiman NS, Hellums JD. Shear-induced platelet aggregation is inhibited by in vivo infusion of an anti-glycoprotein IIb/IIIa antibody fragment, c7E3 Fab, in patients undergoing coronary angioplasty. Circulation. 1995;91:1427–1431.[Abstract/Free Full Text]
  30. Srivatsa SS, Fitzpatrick LA, Tsao TW, Reilly TM, Holmes DR Jr, Schwartz RS, Mousa SA. Selective {alpha}vß3 integrin blockade potently limits neointimal hyperplasia and lumen stenosis following deep coronary arterial stent injury: evidence for the functional importance of integrin {alpha}vß3 and osteopontin expression during neointima formation. Cardiol Res. 1997;36:408–428.
  31. Giachelli CM, Bae N, Almeida M, Denhardt DT, Alpers CE, Schwartz SM. Osteopontin is elevated during neointima formation in rat arteries and is a novel component of human atherosclerotic plaques. J Clin Invest. 1993;92:1686–1696.
  32. Chen Y-P, O'Toole TE, Leong L, Liu B-Q, Diaz-Gonzalez F, Ginsberg MH. ß3 integrin-mediated fibrin clot retraction by nucleated cells: differing behavior of {alpha}IIbß3. Blood. 1995;86:2606–2615.[Abstract/Free Full Text]
  33. Byzova TV, Plow EF. Networking in the hemostatic system. J Biol Chem. 1997;272:27183–27188.[Abstract/Free Full Text]
  34. Jordan RE, Wagner CL, Gray JW, Bhattacharya S, Sane DC, Machin SJ, Mackie I, Anderson KM, Mattis JA, Weisman HF. Molecular pharmacology of chimeric 7E3 monoclonal Fab fragment in human subjects: Plasma clearance and binding to platelet GP IIb/IIIa receptors. Blood. 1991;78:489A. Abstract.Abciximab has comparable affinity and blocking efficacy for {alpha}vß3 and GP IIb/IIIa in vitro. Abciximab also redistributes in vitro between GP IIb/IIIa and {alpha}vß3 integrins. As an antagonist of both GP IIb/IIIa and {alpha}vß3, abciximab may offer added clinical benefit by preventing {alpha}vß3-mediated effects such as thrombin generation, clot retraction, or smooth muscle cell migration and proliferation. Abciximab has been previously shown to circulate on platelets for up to 2 weeks. These findings suggest that abciximab may continue to inhibit both GP IIb/IIIa and {alpha}vß3 after therapy has ceased.



This article has been cited by other articles:


Home page
J Am Coll CardiolHome page
J. L. Anderson, C. D. Adams, E. M. Antman, C. R. Bridges, R. M. Califf, D. E. Casey Jr, W. E. Chavey II, F. M. Fesmire, J. S. Hochman, T. N. Levin, et al.
ACC/AHA 2007 Guidelines for the Management of Patients With Unstable Angina/Non-ST-Elevation Myocardial Infarction: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 2002 Guidelines for the Management of Patients With Unstable Angina/Non-ST-Elevation Myocardial Infarction) Developed in Collaboration with the American College of Emergency Physicians, the Society for Cardiovascular Angiography and Interventions, and the Society of Thoracic Surgeons Endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation and the Society for Academic Emergency Medicine
J. Am. Coll. Cardiol., August 14, 2007; 50(7): e1 - e157.
[Full Text] [PDF]


Home page
HeartHome page
V K Bhatia and C Di Mario
Darwin and the survival of the fittest in modern interventional cardiology
Heart, August 1, 2006; 92(8): 1017 - 1018.
[Abstract] [Full Text] [PDF]


Home page
J Am Coll CardiolHome page
W. Kim, M. H. Jeong, K. H. Kim, I. S. Sohn, Y. J. Hong, H. W. Park, J. H. Kim, Y. K. Ahn, J. G. Cho, J. C. Park, et al.
The Clinical Results of a Platelet Glycoprotein IIb/IIIa Receptor Blocker (Abciximab: ReoPro)-Coated Stent in Acute Myocardial Infarction
J. Am. Coll. Cardiol., March 7, 2006; 47(5): 933 - 938.
[Abstract] [Full Text] [PDF]


Home page
Am. J. Pathol.Home page
Z. Touat, V. Ollivier, J. Dai, M.-G. Huisse, A. Bezeaud, U. Sebbag, T. Palombi, P. Rossignol, O. Meilhac, M.-C. Guillin, et al.
Renewal of Mural Thrombus Releases Plasma Markers and Is Involved in Aortic Abdominal Aneurysm Evolution
Am. J. Pathol., March 1, 2006; 168(3): 1022 - 1030.
[Abstract] [Full Text] [PDF]


Home page
Eur Heart J SupplHome page
M. Ferenc and F.-J. Neumann
Efficacy of primary PCI: the microvessel perspective
Eur. Heart J. Suppl., October 1, 2005; 7(suppl_I): I4 - I9.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
P. Chen, C.-X. Sun, and J.-N. Liu
A Novel Anti-platelet Monoclonal Antibody (3C7) Specific for the Complex of Integrin {alpha}IIb{beta}3 Inhibits Platelet Aggregation and Adhesion
J. Biol. Chem., July 8, 2005; 280(27): 25403 - 25408.
[Abstract] [Full Text] [PDF]


Home page
CirculationHome page
W.H. W. Tang and A. M. Lincoff
Diabetes, Coronary Intervention, and Platelet Glycoprotein IIb/IIIa Blockade: The Triad Revisited
Circulation, December 14, 2004; 110(24): 3618 - 3620.
[Full Text] [PDF]


Home page
CirculationHome page
J. Mehilli, A. Kastrati, H. Schuhlen, A. Dibra, F. Dotzer, N. von Beckerath, H. Bollwein, J. Pache, J. Dirschinger, P. P. Berger, et al.
Randomized Clinical Trial of Abciximab in Diabetic Patients Undergoing Elective Percutaneous Coronary Interventions After Treatment With a High Loading Dose of Clopidogrel
Circulation, December 14, 2004; 110(24): 3627 - 3635.
[Abstract] [Full Text] [PDF]


Home page
CirculationHome page
A. J. Chaves, A. G.M.R. Sousa, L. A. Mattos, A. Abizaid, R. Staico, F. Feres, M. Centemero, L. F. Tanajura, A. Abizaid, I. Pinto, et al.
Volumetric Analysis of In-Stent Intimal Hyperplasia in Diabetic Patients Treated With or Without Abciximab: Results of the Diabetes Abciximab steNT Evaluation (DANTE) Randomized Trial
Circulation, February 24, 2004; 109(7): 861 - 866.
[Abstract] [Full Text] [PDF]


Home page
EuropaceHome page
C. Kouakam, S. Kacet, J.-R. Hazard, A. Ferraci, H. Mansour, P. Defaye, J.-M. Davy, M. Lambiez, and on behalf of the Ventak AV Investigators
Performance of a dual-chamber implantable defibrillator algorithm for discrimination of ventricular from supraventricular tachycardia
Europace, January 1, 2004; 6(1): 32 - 42.
[Abstract] [Full Text] [PDF]


Home page
Eur Heart JHome page
S. J. Brener, S. G. Ellis, J. Schneider, C. Apperson-Hansen, and E. J. Topol
Abciximab-facilitated percutaneous coronary intervention and long-term survival--a prospective single-center registry
Eur. Heart J., April 1, 2003; 24(7): 630 - 638.
[Abstract] [Full Text] [PDF]


Home page
CirculationHome page
A. M. Lincoff
Important Triad in Cardiovascular Medicine: Diabetes, Coronary Intervention, and Platelet Glycoprotein IIb/IIIa Receptor Blockade
Circulation, March 25, 2003; 107(11): 1556 - 1559.
[Full Text] [PDF]


Home page
Eur Heart J SupplHome page
F.-J. Neumann and N. Jander
How to best counteract the enemies? By ensuring adequate oxygen delivery
Eur. Heart J. Suppl., November 1, 2002; 4(suppl_G): G35 - G42.
[Abstract] [PDF]


Home page
Cancer Res.Home page
M. Trikha, Z. Zhou, J. Timar, E. Raso, M. Kennel, E. Emmell, and M. T. Nakada
Multiple Roles for Platelet GPIIb/IIIa and {alpha}v{beta}3 Integrins in Tumor Growth, Angiogenesis, and Metastasis
Cancer Res., May 1, 2002; 62(10): 2824 - 2833.
[Abstract] [Full Text] [PDF]


Home page
CirculationHome page
P. N. Seshiah, D. J. Kereiakes, S. S. Vasudevan, N. Lopes, B. Y. Su, N. A. Flavahan, and P. J. Goldschmidt-Clermont
Activated Monocytes Induce Smooth Muscle Cell Death: Role of Macrophage Colony-Stimulating Factor and Cell Contact
Circulation, January 15, 2002; 105(2): 174 - 180.
[Abstract] [Full Text] [PDF]


Home page
NeurologyHome page
D. J. Fintel
From bench to bedside: GP IIb-IIIa inhibitors
Neurology, September 1, 2001; 57(90002): S12 - 19.
[Abstract] [Full Text]


Home page
NeurologyHome page
J. Bogousslavsky and J. R. Leclerc
Platelet glycoprotein IIb/IIIa antagonists for acute ischemic stroke
Neurology, September 1, 2001; 57(90002): S53 - 57.
[Abstract] [Full Text]


Home page
CirculationHome page
M. Lele, M. Sajid, N. Wajih, and G. A. Stouffer
Eptifibatide and 7E3, but Not Tirofiban, Inhibit {alpha}v{beta}3 Integrin-Mediated Binding of Smooth Muscle Cells to Thrombospondin and Prothrombin
Circulation, July 31, 2001; 104(5): 582 - 587.
[Abstract] [Full Text] [PDF]


Home page